Decomposition of the vertical ground reaction forces during gait on a single force plate

Davis and Cavanagh (1993) have proposed a solution to avoid the footstep targeting by using a large force plate but several points of Davis and Cavanagh's method remain unclear and hardly computable. Objective: to develop a method that decomposes left and right GRF profiles from the GRF profile recorded on a single platform. This method aims to include a systematic detection of the single to double stand-phase-instants in order to lead to accurate measurement of the vertical GRF component in typically developing children. Methods: Six children were asked to walk without targeting their footsteps on a set-up composed of independent force platforms. The vertical GRF component, independently measured on the different platforms, was numerically summed to obtain the corresponding global vertical GRF, to which the decomposition method was applied. Then, the validation consisted in comparing the vertical GRF computed from this decomposition to the independently measured vertical GRF. Results: the mean relative error between the computed vertical GRF and the corresponding measured vertical GRF of 36 double stances (6 double stances x 6 children) is equal to 3.8+/-2.6 %. Conclusion: implemented a new method to assess with known accuracy the vertical GRF component under each foot using a unique large force platform.